Roadway surfaces and bridges experience stresses due to the weight of load-bearing vehicles which travel the roadway systems. To lessen the detrimental effect of such traffic on the roadway systems, federal and state laws regulate load-bearing vehicles which travel federal and state roadways. These regulations dictate maximum loading per vehicle axle, which is based on the load-bearing capacity of roadway surfaces in the system, and minimum distance between load-bearing axles, which ensures that the vehicle's load is properly distributed over individual structural members of a bridge in the roadway system. Thus, vehicle weight restrictions generally are specified as a combination of load per axle and distance between axles.
To comply with such regulations, work vehicles that are designed to carry a substantial load often include some type of auxiliary axle that increases the vehicle's legal load-carrying capacity. Auxiliary axles generally include pusher axles, which typically are mounted forward of the vehicle's rear drive axle, and trailer or tag axles, which are mounted aft of the rear axle. Such auxiliary axles increase load-bearing capacity by redistributing the load on the vehicle's axles and/or extending the wheel base between load-bearing axles.
Pusher axles and many tag axles typically are deployable between a lifted or stowed position and a lowered or load-bearing position. Stowable configurations for tag axles generally employ hydraulically actuated piston assemblies that vertically pivot the axle relative to the vehicle to raise and lower the device. In the stowed position, the tag axle typically is positioned in a raised position at the rear of the vehicle. For some vehicles, tag axles in the stowed position can hinder loading and unloading tasks, thus rendering such arrangements impractical or unusable, particularly for vehicles have a flat loading bed.
Other trailer or tag axles may be configured as a detachable assembly. Typically, such assemblies include a pivotable connection that allows the assembly to pivot transversely relative to the vehicle such that the trailer axle can track behind the vehicle when turning. For some vehicles, however, transverse movement of the trailer relative to the vehicle can have detrimental effects on the stability of the vehicle during a turn as a result of the forces exerted by the trailer axle assembly on the vehicle frame which are necessary to redistribute the load on the axles. Further, transverse movement hinders maneuvers in a reverse direction. Thus, although a detachable trailer axle assembly does not present an obstacle to loading/unloading operations, other issues with respect to vehicle stability and maneuverability may arise.
Accordingly, it would be desirable to provide an auxiliary axle assembly that overcomes the aforementioned disadvantages of known auxiliary axle assemblies.